Lung cancer is the leading cause of death of both men and women in industrialized countries, accounting for an estimated 28% of all cancer deaths in the United States. Non-small cell lung cancers (NSCLC) represent the majority of lung cancers and carry a poor prognosis with a median survival of less than 12 months. Most patients present with unresectable disease, and the current treatment options of chemotherapy and radiation are palliative at best. Therefore, new strategies are needed in the treatment of NSCLC in order to impact the severity of this disease. In this study, we are focusing on NSCLC models for examining distal signaling mechanisms that modulate the development and maintenance of NSCLC cells/tumors. Specifically, this grant application focuses on the RNA splicing events regulated by the phosphorylation/activation of the RNA trans-factor, hnRNP L, which occurs only in transformed cells. In stark contrast with our findings on the phosphorylation of Ser52 in hnRNP L in transformed cells, downregulation of hnRNP L in non-transformed cells had no effect on RNA splicing events important in maintaining oncogenic phenotypes (e.g. anchorage-independent growth (AIG)). Further investigations by our laboratory determined that the lack of effect on RNA splicing events in non-transformed cells was due to a lack of phosphorylation of Ser52 in hnRNP L. Thus, these findings suggest that the phosphorylation of hnRNP L (i.e. activation in transformed cells) mediates specific RNA splicing events important in cell survival, proliferation, and AIG versus constitutive functions of non-phosphorylated hnRNP L. Therefore, we hypothesize that the phosphorylation of hnRNP L on Ser52 is required for modulating a specific subset of splicing events, which are important for NSCLC cells to develop and maintain transformed phenotypes. The proposed studies in this application serve to determine the specific ?cluster? of RNA splicing events regulated by the phosphorylation of hnRNP L. Once identified, we will further investigate the biological relevance of these RNA splicing events in maintaining the oncogenic phenotypes of NSCLC cells. The key mechanisms being examined in this grant application are specific to transformed cells, translatable to >70% of NSCLCs, and at an extreme distal point in oncogenic pathways. Therefore, these distal mechanisms are plausible and highly desired targets for the development of new anti-cancer therapeutics.